Today the Institute of Medicine, a very cautious body, released its report from IOM, Breast Cancer and the Environment: A Life Course Approach.

It concluded, "Although the overall magnitude of the reported effect of exposure to active or passive smoking on risk for breast cancer is not large, some susceptible subgroups appear to have a relative risk that is elevated over that of never smokers. Evidence of an increased risk for breast cancer reinforces the importance of smoking prevention and cessation programs and policies supporting smoke-free environments." (page 3-26)

It's time for the large breast cancer advocacy groups to join the tobacco control community.

WASHINGTON — Women may be able to reduce their risk for breast cancer by avoiding unnecessary medical radiation, forgoing use of combination estrogen-progestin menopausal hormone therapy if possible, limiting alcohol consumption, maintaining a healthy weight, exercising regularly, and avoiding tobacco use, says a new report from the Institute of Medicine. These preventive steps focus on the environmental risk factors for which there is consistent scientific evidence of an association with breast cancer.

The evidence also indicates a possible, though currently less clear, link to increased risk for breast cancer from exposure to benzene, 1,3-butadiene, and ethylene oxide, which are chemicals found in some workplace settings and in gasoline fumes, vehicle exhaust, and tobacco smoke. Avoiding personal use of hair dyes and non-ionizing radiation emitted by mobile devices and other technologies likely will not impact a woman's risk for breast cancer, as multiple studies have found no connection to the disease.

Because of insufficient or contradictory evidence, the scientific jury is still out on whether many chemicals of concern, including bisphenol A (BPA), pesticides, ingredients in cosmetics and dietary supplements, and other substances alter the risk for breast cancer, the report says. Women may choose to minimize their exposure to some chemicals, but the committee found the research inadequate to draw conclusions about the potential benefit of such actions. Chemical ingredients in cosmetics, dietary supplements, and other products undergo only very limited testing before they are put on the market, and the committee noted the value of efforts to help consumers become more aware of this issue.

The steps identified in the report have the potential to reduce risk for breast cancer among women in general, but the committee cautioned that the evidence on how much risk reduction any of these steps offers is inconclusive. Whether it is small or significant, the impact on individuals will vary considerably because women are exposed to a range of substances throughout their lives; in addition, biological, physical, and genetic factors influence their individual chances for developing the disease.

The report's conclusions are the result of a detailed review of scientific research on environmental factors that may affect breast cancer risk. The committee also explored challenges to studying possible links between environmental exposures and breast cancer and recommends future research directions. Areas where there is provocative but as yet inconclusive evidence and that warrant priority attention include overnight shift work and accompanying disruptions of the sleep cycle; chemicals that mutate genes, alter gene expression, or affect hormones such as estrogen; and gene-environment interactions. More research needs to be conducted on the effects of exposures throughout the entire life span, including at specific stages of breast development, and on the cumulative effects of exposures at different life stages or multiple exposures that occur together, the report emphasizes. Most research has focused on adults and on exposures occurring within a few years prior to a diagnosis, but recent studies have shown the importance of exposures at various life stages, such as childhood, adolescence, pregnancy, and menopause.

In many cases, more information also needs to be gathered to determine whether preventive steps can be taken and how they can be most effective. For example, we do not yet know when weight loss is most likely to be beneficial in reducing postmenopausal cancer risk.

"Breast cancer develops over many years, so we need better ways to study exposures throughout women's lives, including when they are very young," said committee chair IrvaHertz-Picciotto, professor, department of public health sciences, and chief, division of environmental and occupational health, School of Medicine, University of California, Davis. "We also need improved methods to test for agents that may be contributing to breast cancer risk and to explore the effects of combined exposures."

The study was sponsored by Susan G. Komen for the Cure. Established in 1970 under the charter of the National Academy of Sciences, the Institute of Medicine provides independent, objective, evidence-based advice to policymakers, health professionals, the private sector, and the public. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. For more information, visit http://national-academies.org or http://iom.edu. A committee roster follows.

# # #

INSTITUTE OF MEDICINE

Board on Health Care Services and Board on Health Sciences Policy

Committee on Breast Cancer and the Environment: The Scientific Evidence, Research Methodology, and Future Directions

IrvaHertz-Picciotto, Ph.D., M.P.H. (chair)

Professor and Chief

Division of Environmental and Occupational Health

Department of Public Health Sciences

University of California

Davis

Lucile L. Adams-Campbell, Ph.D., M.S.

Professor of Oncology, and

Associate Director for Minority Health and Health Disparities Research